botulinum toxin type A

botulinum toxin type A

Botox, Botox Cosmetic, Dysport (UK), Vistabel (UK)

Pharmacologic class: Neurotoxin

Therapeutic class: Neuromuscular blocker

Pregnancy risk category C

Action

Blocks neuromuscular transmission by binding to receptor sites on motor nerve terminals and inhibiting acetylcholine release, thereby causing localized muscle denervation. As a result, local muscle paralysis occurs, which leads to muscle atrophy and reinnervation due to development of new acetylcholine receptors.

Availability

Toxin type A -

Powder for injection: 100 units/vial

Toxin type B -

Solution for injection: 5,000-units/ml vial

⊘Indications and dosages

Toxin type A

➣ Temporary improvement in appearance of moderate to severe glabellar lines associated with corrugator or procerus muscle activity

Adults ages 65 and younger: Botox cosmetic only - Total of 20 units (0.5-ml solution) injected I.M. as divided doses of 0.1 ml into each of five sites: two in each corrugator muscle and one in procerus muscle. Injection usually needs to be repeated q 3 to 4 months to maintain effect.

➣ Blepharospasm

Adults: 1.25 to 2.5 units injected into medial and lateral pretarsal orbicularis oculi of upper eyelid and lateral pretarsal orbicularis oculi of lower eyelid

➣ Strabismus

Adults: 1.25 to 5 units injected into eyelid (dosage varies with strabismus severity). Dose can be repeated in 7 to 14 days if patient has adequate response; with inadequate response, dosage may be doubled.

Toxin types A and B

➣ To relax skeletal muscles and reduce severity of abnormal head position and neck pain associated with cervical dystonia

Adults: Botox - Usual dosage is 236 units injected I.M. locally into affected muscles. Dosage ranges from 198 to 300 units. Myobloc - 2,500 to 5,000 units I.M. injected locally into affected muscles.

Contraindications

• Hypersensitivity to drug
• Active infection at injection site

Precautions

Use cautiously in:
• cardiovascular disease, peripheral neuropathy, neuromuscular disorders
• inflammation at injection site
• pregnant or breastfeeding patient.
• children younger than age 12.

Administration

Toxin type A
• Reconstitute toxin type A by slowly injecting preservative-free normal saline solution into drug vial.
• Rotate vial gently to mix drug; then draw up at least 20 units (0.5-ml solution) and expel air bubbles.
• Remove needle used for reconstitution, and attach 30G needle. Then inject drug as divided doses of 0.1 ml into each of five sites (two in each corrugator muscle, one in procerus muscle).
• Prepare eye with several drops of local anesthetic and ocular decongestant, as prescribed, several minutes before injection for blepharospasm or strabismus.
• Be aware that only trained medical personnel should inject this drug.

Toxin type B
• Draw up prescribed dose from preservative-free, 3.5-ml single-use vial.
• Don't shake vial.
• Divide prescribed dose and inject locally into affected muscles.

Route	Onset	Peak	Duration
I.M.	Mins-hrs	Unknown	3-4 mo
I.M. (blepharospasm)	3 days	1-2 wk	3 mo
I.M. (strabismus)	1-2 days	Unknown	1-2 wk

Adverse reactions

CNS: headache, dizziness

CV: hypertension, arrhythmias, myocardial infarction (MI)

EENT: blepharoptosis, conjunctivitis, keratitis, eye dryness, double vision, tearing, increased sensitivity to light, sinusitis, pharyngitis

GI: nausea, dyspepsia, difficulty swallowing

Musculoskeletal: back pain, neck pain, muscle weakness

Respiratory: pneumonia, bronchitis, upper respiratory tract infection

Skin: skin tightness, ecchymosis

Other: tooth disorder; injection site redness, edema, or pain; flulike symptoms; facial muscle paralysis; infection;

anaphylaxis

Interactions

Drug-drug. Aminoglycosides, anticholinesterase compounds, clindamycin, lincomycin, magnesium sulfate, other neuromuscular blockers (such as succinylcholine), polymyxin B, quinidine: increased risk of adverse effects

Patient monitoring

• Stay alert for signs and symptoms of anaphylaxis, particularly after first dose.
• Monitor vital signs and ECG, watching for evidence of hypertension, arrhythmias, and MI.
• Assess effect of drug on affected muscles; check for paralysis.
• Monitor temperature. Watch for signs and symptoms of respiratory and EENT infections as well as flulike symptoms.

Patient teaching

• Teach patient about desired effect of injection. Advise patient to report paralysis.
• Instruct patient to report signs and symptoms of infection, particularly flulike illness and EENT and respiratory infections.
• Inform patient being treated for blepharospasm (uncontrollable blinking) that he may experience transient eyelid drooping, corneal inflammation, double vision, dry eyes, tearing, and light sensitivity.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs mentioned above.